JPH11-247990A, published by the Japan Patent Office in 1999, discloses a hydraulic servo mechanism that varies a swash plate tilt angle to vary a capacity of a swash plate hydraulic pump.
JP2005-105898A, published by the Japan Patent Office in 2005, discloses an opposing swash plate hydraulic pump/motor in which a first swash plate and a second swash plate are disposed on either side of a cylinder block to face each other. A first piston that contacts the first swash plate in a state where it is free to slide and a second piston that contacts the second swash plate in a state where it is free to slide, are housed in respective cylinders of the cylinder block.
In accordance with rotation of the cylinder block, the first piston is driven in an axial direction by the first swash plate and the second piston is driven in the axial direction by the second swash plate, and thus the first piston and second piston reciprocate within the cylinder. By varying the tilt angles of the two swash plates, the capacity can be varied more widely than in a hydraulic pump/motor that uses a single swash plate.